The timing of an internal combustion engine must be accurately controlled so that emissions are minimized and so that the engine runs at peak efficiency. In compression type diesel engines, ignition occurs upon injection of fuel into a cylinder containing air that has been compressed by a piston which is movable in the cylinder. The "timing" of such an engine is defined as the time at which a fuel injector is operated to inject fuel into the cylinder relative to the time at which the piston reaches a position known as "top dead center" in the cylinder that has reached the end of the piston stroke. Current state of the art engines typically include electronically controlled fuel injectors, which provides for efficient engine operation at maximum power.
In such engines that utilizes electronic fuel injectors, the position of the piston within the cylinders relative to top dead center must be measured. These measurements must be accurate in order to maximize engine operating efficiency. However, once the highly accurate measurement system fails, the entire engine control will shutdown. Consequently, it is desirable to introduce redundancy into the system in order to prevent catastrophic failure of the engine control system.
The present invention is directed toward overcoming one or more of the problems as set forth above.